The Douglas C-54 Skymaster is a four-engined transport aircraft used by the United States Army Air Forces in World War II and the Korean War. Like the Douglas C-47 Skytrain, the C-54 Skymaster was derived from a civilian airliner, the Douglas DC-4. Besides transport of cargo, the C-54 also carried presidents, prime ministers, and military staff. Dozens of variants of the C-54 were employed in a wide variety of non-combat roles such as air-sea rescue, scientific and military research, and missile tracking and recovery. During the Berlin Airlift it hauled coal and food supplies to West Berlin. After the Korean War it continued to be used for military and civilian uses by more than 30 countries. This was one of the first aircraft to carry the President of the United States.

With the entry of the United States into World War II, in June 1941 the War Department took over the provision orders for the airlines for the Douglas DC-4 and allocated them to the United States Army Air Forces with the designation C-54 Skymaster. The first, a C-54, flew from Clover Field in Santa Monica, California on 14 February 1942.

To meet military requirements the first civil production aircraft had four additional auxiliary fuel tanks in the main cabin which reduced the passenger seats to 26. The following batch of aircraft, designated C-54A, were built with a stronger floor and a cargo door with a hoist and winch. The first C-54A was delivered in February 1943. The C-54B, introduced in March 1944, had integral fuel tanks in the outer wings, allowing two of the cabin tanks to be removed. This change allowed 49-seats (or 16 stretchers) to be fitted. The C-54C, a hybrid for Presidential use, had a C-54A fuselage with four cabin fuel tanks and C-54B wings with built in tanks to achieve maximum range.

The most common variant was the C-54D, which entered service in August 1944. Based on the C-54B, it was fitted with more powerful R-2000-11 engines. With the C-54E, the last two cabin fuel tanks were moved to the wings which would allow more freight or 44 passenger seats.

C-54s began service with the USAAF in 1942, carrying up to 26 passengers, later versions carrying up to 50 passengers. The C-54 was one of the most commonly used long-range transports by the U.S. armed forces in World War II. Of the C-54s produced, 515 were manufactured in Santa Monica, California and 655 were manufactured at Orchard Place/Douglas Field, in unincorporated Cook County, Illinois, near Chicago (later the site of O'Hare International Airport).[1]

In late 1945, several hundred C-54s were surplus to U.S. military requirements and these were converted for civil airline operation, many by Douglas Aircraft at its aircraft plants. The aircraft were sold to airlines around the world. By January 1946, Pan American Airways was operating their Skymasters on transatlantic scheduled services to Europe and beyond. Trans-Pacific schedules from San Francisco to Auckland began on 6 June 1946.[4] After disposal by the U.S. Air Force and U.S. Navy, many C-54s were modified for use in civilian firefighting and air tanker roles. This included fitting tanks inside and under the fuselage and the fitting of dumping and spraying equipment also on the wing trailing edges. C-54s continued in this role until the late 1990s.

On 29 April 1952, an Air France Douglas C-54A (registration F-BELI) operating a scheduled service from Frankfurt Rhein-Main Airport to Berlin Tempelhof Airport came under sustained attack from two Soviet MiG 15fighters while passing through one of the Allied air corridors over East Germany. Although the attack had severely damaged the aircraft, necessitating the shutdown of engines number three and four, the pilot in command of the aircraft managed to carry out a safe emergency landing at Tempelhof Airport. A subsequent inspection of the aircraft's damage revealed that it had been hit by 89 shots fired from the Soviet MiGs. There were no fatalities among the 17 occupants (six crew, 11 passengers) despite the severity of the attack. The Soviet military authorities defended this attack on an unarmed civilian aircraft by claiming the Air France plane was outside the air corridor at the time of attack.[8]